At present, demands from people for mobile communications are not limited to telephone and message services, with the rapid development of the Internet, a plenty of multimedia services have emerged. In some of the services, multiple users enable to receive the same data synchronously, such as video on demand, television broadcast, video conference, online education, interactive game and the like. A multimedia broadcast multicast service (MBMS) technology is proposed for the most effective utilization of mobile network resources, in this technology, a point-to-multipoint service in which a data source sends data to multiple users realizes the share of network resources, including the share of mobile core network resources and access network resources, and especially, interface resources. An MBMS defined by the 3rd generation partnership project (3GPP) can realize not only multicast and broadcast of plain text messages at low speed but also multicast and broadcast of multimedia services at high speed, which undoubtedly conforms to the future trend of mobile data development.
As a technology for improving the spectrum utilization rate of an MBMS, an MBMS single frequency network (MBSFN) technology requires all adjacent base stations to send the same radio signals synchronously, and a user equipment (UE) may take signals from different base stations as multi-path signals, in this way, a great signal gain can be obtained during broadcast service transmission through a common physical channel, and consequently, the quality of service (QoS) of an MBSM service can be improved. A group of cells that send MBMS radio signals synchronously form an MBSFN synchronization area and are known as MBSFN cells. The cells in the MBSFN synchronization area synchronously send the same radio signals including MBMS signals, all or part of system messages, point-to-multipoint control channel messages (MCCH messages), and MBMS notification indicator channel (MICH) messages.
In a 3GPP UTRAN (universal mobile telecommunication systems (UMTS) terrestrial radio access network) architecture protocol, a system message consists of information blocks (IB), which are functionally classified into a master information block (MIB), a scheduling information block and a system information block. When these information blocks are transmitted via radio interfaces, they are further divided into multiple segments, and these segments are further classified in terms of type into a first segment, a middle segment, a last segment, an integral segment and the like and are sent according to scheduling, and the time for sending each segment can be determined according to the following formula: SFN mod repetition period=segment location.
In a 3GPP long term evolution (LTE) architecture, the following change is made on scheduling of information blocks: a scheduling unit (SU) is defined, and one or more information blocks are mapped into one scheduling unit.
According to the definition of existing protocols of the 3GPP, the MCCH is a logical channel, an MCCH message includes a series of MBMS control messages, scheduling information of which includes a modification period and a repetition period, and in one modification period, an MCCH message is sent via a radio interface for many times according to a repetition period, while the contents of the message can not be modified in the modification period; for the sake of synchronization, a repetition period and modification period of a cell should be identical with those of other cells.
According to the definition of existing protocols of the 3GPP, the MICH is a physical channel for notifying a UE of the change of an MBMS in an MCCH message.
The following is an existing networking technology adopting MBSFN carrier frequency:
In a time division-synchronous code division multiple access (TD-SCDMA) technology, a networking technology using MBSFN-dedicated carrier frequency is adopted, in which all the physical channels in all time slots on a frequency are synchronous with physical channels in time slots on the same frequency of an adjacent cell in terms of contents and time, wherein system messages, MCCH messages and MICH messages of the adjacent cell are also required to be sent synchronously.
In a wideband code division multiple access (WCDMA) technology, signals of all the channels in a cell adopting an MBSFN networking are required to be synchronous with contents and time of physical channels on the same frequency of an adjacent cell, wherein it is also necessary to send system messages, MCCH messages and MICH messages of the adjacent cell synchronously.
In a frequency division duplex (FDD) high speed packet access plus (HSPA+) technology, signals of all the channels in a cell adopting an MBSFN networking are required to be synchronous with contents and time of physical channels on the same frequency of an adjacent cell, wherein it is also necessary to send system messages, MCCH messages and MICH messages of the adjacent cell synchronously.
In an LTE system, cells adopting an MBSFN networking are required to synchronously send the same radio signals of the same radio resource blocks on the same frequency, and system messages thereof are classified into global system messages and local system messages, wherein the global system messages and the MCCH messages in the MCCH MBSFN area are required to be sent synchronously.
All the technologies above refer to the circumstances that adjacent cells are required to send all or part of radio interface control messages synchronously.
Moreover, an MBMS is oriented to the whole network, the same MBMS may be established on nodes of different distributed network elements, therefore cells among these nodes of different distributed network elements are also required to send all or part of system messages of the cells synchronously, otherwise, a UE cannot obtain a reception gain when receiving the system messages, which may result in strong co-channel interference.
The following is a method for realizing MBSFN synchronization among multiple network elements in related technologies.
FIG. 1 is an example diagram of an MBMS synchronization networking according to the UTRAN architecture of TD-SCDMA and WCDMA of related technologies. As shown in FIG. 1, a master radio network controller (RNC) is connected with multiple slave RNCs via lur interfaces, the master RNC (e.g. SRNC) and slave RNC1 (e.g. DRNC1) are connected with serving general packet radio service supporting node-1 (SGSN-1) via lu interfaces, slave RNCn (DRNCn) is connected with SGSN-2 via an lu interface, the slave RNC1 is connected with base station-1 (NodeB-1), the master RNC is connected with base station-2 (NodeB-2), and the slave RNCn is connected with base station-3 (NodeB-3).
FIG. 2 is an example diagram of an MBMS synchronization networking according to the HSPA+ flat architecture of related technologies. As shown in FIG. 2, a master base station+ (master Node B+, or RNC) is connected with one or more slave base stations+ (slave Node B+) via lur interfaces, and the master Node B+ or the RNC is connected with SGSN-1. The full name of MGW is media gateway.
FIG. 3 is an example diagram of an MBMS synchronization networking according to the E-UTRAN architecture of LTE of related technologies. As shown in FIG. 3, a logical network element (e.g. a multi-cell/multicast coordination entity, MCE) is connected with one or more evolved universal mobile telecommunication systems (UMTS) terrestrial radio access network base stations (E-UTRAN Node B, ENB) via M2 interfaces.
In existing technologies, common control messages of each cell, such as system messages, MCCH messages, and MICH messages, are respectively constructed on each network element node and scheduled and sent; if an MBSFN area exceeds the range of a cell where a network element is located and there is no coordination mechanism for cells where multiple network elements are located, then it is difficult or even impossible to realize synchronization of radio interface control messages of these cells. For a UE, radio interface control messages of MBSFN cells cannot be sent and received in an MBSFN manner, thus bringing about strong interference among adjacent cells.
However, existing technologies do not provide a coordination mechanism for multiple network elements on the same layer which coordinate transmission of an MBMS, e.g., lacking a technical solution for coordination between a master RNC and a slave RNC, or between an MCE and an ENB in LTE, and no effective solution has currently been proposed for addressing this problem.